IGFBP4 and cancer: Since the IGF axis could contribute to cancer progression and invasion, it is now widely accepted that aberrant methylation of IGFBP7, IGFBP-4, IGFBP-3, IGF-1R, IGF-1, and IGF-II promoters could be a potential factor in various common human cancers (Qian et al., 2011; Sato et al., 2011; Bolomsky et al., 2015; Ye P. et al., 2016).